1. Field of the Invention
This invention relates generally to an automated machine tool and more particularly to an automated machine tool having a special machine head capable of adjusting the cutting radius of the cutting tool. Another object of this invention provides a machine head that maintains a constant cutter feed rate in surface feet per minute regardless of the distance of the cutting tool from the centerline of rotation.
2. Description of the Prior Art
Traditionally, numerically controlled machine tools have been generally comprised of a support frame having a moveable worktable, moveable in two perpendicular axes, latitudinally and longitudinally in a horizontal plane. A drive head mounted on the support frame above the horizontal worktable, moves on a vertical axis perpendicular to the horizontal worktable, and supports a rotating spindle with a cutting tool attached thereto. The cutting tool is rotated at a fixed speed rate by the spindle and is lowered by the drive head to machine a workpiece supported on the worktable. Precision cutting is performed, such that the center of a hole is precisely located with respect to the vertical axis of the rotating cutting tool and the combined movement of the worktable in its horizontal plane of movement. During the machining operation, the spindle is rotated at a pre-selected cutting speed and is fed downwardly by the drill head on the quill at a predetermined feed rate.
It is desirable for special machining operations to vary the cutting radius of the cutting tool to machine conical or spherical cavities. A cutting tool with such capability has been attempted with a limited amount of success. See U.S. Pat. No. 3,592,553, issued to Charles K. Heizer, on July 13, 1971 in which a boring tool assembly is disclosed having a means to adjust the rotational radius of the cutting tool. A moveable vertical shaft member is designed to create movement of a horizontal shaft member along a guide track to move the cutting tool inwardly or outwardly with respect to the rotational axis of the spindle.
It would be desirable if there were provided an automatic machine tool that varied the cutting rate of the machine tool and provided a means for maintaining a constant cutter feed rate in surface feet per minute, regardless of the distance of the cutting tool from the centerline of rotation.